'Custer's last flag' from Little Bighorn auctions at Sotheby's New York

An item billed as "the most significant and symbolic artefact recovered from the Little Bighorn battlefield" will be auctioned by Sotheby's: the only flag flown by Custer's battalion known not to have been captured by Indian combatants.

Custer's flag has come to market after the recent discovery of letters and manuscripts documenting its traditional story and recovery, as written by troopers of the Seventh Cavalry

The Seventh Cavalry entered the Battle of Little Bighorn with a total of 14 flags; one for each Company A-M, a Seventh Cavalry Silk Regimental Standard flag and the rumoured Custer's personal Guidon.

Of these, two are in national possession (at the Museum) while 11 were presumed to have been taken at the Battle by Indians. This flag, a 35 star guidon, was carried by Company C captained by Thomas Custer (pictured top right) himself.

Custer's flag's provenance is known through recently-discovered documents

Today, the Battle of Little Bighorn is regarded as the central event of the Indian Wars that raged across the Great Plains from the 1860s to the 1880s. Near the River Little Bighorn, Custer divided his Seventh Cavalry up into three groups with the intent of attacking.

Custer was entirely unprepared for the force his men encountered. Encountering possibly as many as 1,800 American Indian warriors, 258 officers and men were killed from the Seventh Cavalry alone, and everyone under Custer's immediate command including scouts and civilians.

In fact, the flag was clipped away by surviving members of the Seventh Cavalry who discovered it as souvenirs - a common practice after battle.

Aside from the story attached to it, the flag is especially remarkable because not many physical artefacts were left on the battlefield. The flag of Company I (Captain Myles Keogh) is at the Little Bighorn Battlefield Museum, as is the Seventh Cavalry Regimental Standard flag.

A dramatic reconstruction of Custer being stabbed by Chief Sitting Bull

Sotheby's describes the flag as a "silk guidon with a field of 13 red and white strips and a canton of blue with 35 applied gold stars, with a swallow-tail design at [its] free edge." Its condition includes fraying, splits, tears and running of colour.

Actually, the recently-discovered documents relating to the flag clear up many mysteries and untruths regarding its condition. Charles C Colbraith, a patriotic retired major, wrote an account describing a section of the flag "wrenched away probably by some savage hand."